1. Field of the Invention
The present disclosure relates to a sheet processing apparatus and an image forming apparatus. In particular, the present disclosure relates to a configuration for improving a stacking property of sheet bundles which are processed and discharged to a stacking tray.
2. Description of the Related Art
Conventionally, there is an image forming apparatus, such as a copying machine, a laser beam printer, a facsimile, and a multifunction peripheral including functions of such devices, which includes a sheet processing apparatus. The sheet processing apparatus performs processing such as stapling, punching, and sorting with respect to sheets on which images are formed. Further, an image forming apparatus (i.e., an image forming system) is widely known, in which the sheet processing apparatus is connected to a discharge port of an image forming apparatus main body, and automatically performs the above-described processing on the sheets online.
A widely-used sheet processing apparatus includes an intermediate processing tray therein, stacks a plurality of sheets on the intermediate processing tray to form a sheet bundle, and staples the sheet bundle. Such a sheet processing apparatus discharges the stapled sheet bundle from a discharge port to a tilted stacking tray (refer to U.S. Pat. No. 5,398,918).
In the conventional sheet processing apparatus, the sheet bundle discharged to the stacking tray slides downwards due to self-weight and the tilt of the stacking tray. The sheet bundle then comes into contact with an alignment wall disposed below the discharge port. As a result, an end of the sheet bundle in an upstream side in a discharging direction becomes aligned, so that a stacking property of the sheet bundles is improved.
However, when the sheet bundle slides downwards, the end of the sheet bundle in the upstream side in the discharging direction may become caught on a stapled portion (i.e., a staple ST) of a sheet bundle SA1 previously stacked on a stacking tray 137 as illustrated in FIG. 21. The sheet bundle may thus not come into contact with an alignment wall 137a, so that the stacking property of sheet bundles SA1 and SA2 on the stacking tray is deteriorated.